The last person to receive a Civil War pension has died. Her name was Irene Triplett. In the article I read about this (see here), it mentioned that her father originally served in the Confederate Army before defecting to serve in the Union Army.
This raised so many questions for me. Besides the questions in the title, I wondered what kind of reception they got on the Union side - were they treated as prodigal sons, or as... prodigal brothers (so to speak)? Did any Union soldiers defect to the Confederacy?
I touched on this a bit in this previous answer of mine. Let me know if you have any follow-ups!
A related question, if I may: Were there instances in the American Civil War of units switching sides during a battle?
(Mods, let me know if you’d prefer me to ask this as a new topic)